The results from the latest studies suggest that ARID1A mutation and the resultant functional deficiency are associated with the elevation in PD-L1 expression and the TMB value in ovarian cancer (Shen et al. 2018) and gastric cancer (Li et al. 2019), which indicates the underlying relationship between ARID1A and potential therapeutic anticancer immunity. The gene discussed is CD274; the disease is gastric cancer.